CS3502:CS3502:

Data and Computer Data and Computer NetworksNetworks

INTRODUCTIONINTRODUCTION

introduction: CS3502introduction: CS3502

overview of computer networks Track

course objectives

homeworks, tests, grading

approximate schedule

objectives: CS3502objectives: CS3502

gain good overview of networking detailed knowledge of

physical layer data link layer local area networks

elementary protocol specification and analysis

elementary performance analysis

homeworks, etc: CS3502homeworks, etc: CS3502

homeworks passed out in class OR in electronic form. NOT GRADED.

solutions for majority of homeworks provided.

3 tests spaced roughly 1/3 of quarter tests based - in order of priority- on

homeworks class notes, lectures text

introduction: CS3502introduction: CS3502

network definitions

classifications

models (high level) ISO model

DOD model

IEEE model

purposes of networks

network industries

communication protocols

Basic TermsBasic Terms Communication

Information

Data

Node

Data Communication

Data Processing

- moving information from one physical node to another

- data

- a pattern of 0’s and 1’s

- a physical system for holding information

- moving data from one physical node to

another

- changing data within a node

Examples of NetworksExamples of Networks

local, long distance telephone networks

computer LANs: ethernet, token ring

ARPANet/MILNET WANs

Cable TV networks

Cellular phone networks

The INTERNET

network definitionsnetwork definitions

Networks

computer network

distributed network

LAN, MAN, WAN

integrated network

internetwork/Internet

network classificationnetwork classification

geographical coverage (LAN ... WAN)

topology

switching technique

speed (data rates)

data/information content

geographical coveragegeographical coverage

LANs simpler, less software layers higher data transfer rates (generally) simple routing IEEE standards easily connected together via bridges examples: ethernet, token ring, FDDI

geographical coveragegeographical coverage

MANs

traditional category

cable TV, local phone

DQDB, FDDI (?)

less used, as most networks can be classified into LAN/WAN

geographical coveragegeographical coverage

WANs data speeds slower, in general (this

distinction fading) national, international boundaries includes internetworking ARPANet first example much more complex software OSI model

network topologiesnetwork topologies

star

ring

bus

fully connected

tree

mesh

switching techniquesswitching techniques

broadcast no switching or routing; 1 station

transmits, all others can receive collisions occur if more than 1 attempts

to transmit at once examples: ethernet LAN and radio

networks, satellites (to some degree)

switching techniquesswitching techniques

circuit switching 3 distinct phases traditional voice network nice for user, but inefficient use of

transmission facilities served traditional voice networks

well, but gradually becoming outdated by new technology

switching techniquesswitching techniques message switching

sends entire message as single transmission

efficiency problems from unbound msg. size

packet switching fixed packet size much more efficient use of facilities several refinements; fast packet switching

(ATM) is culmination

network model: ISO 7-layersnetwork model: ISO 7-layers

designed ~1970; still heavily referenced 7 layer model for networks --

1. physical - moves a bit from a to b using a physical(electrical, optical, etc.) signal

2. data link - groups bits into frames, or messages, for error control and information

3. network - routing function

network model: ISO 7-layersnetwork model: ISO 7-layers

4. transport - end to end; interface between user apps and the network/internet

5. session, presentation - ??

7. application - user interface to network, and user services: email, file transfer, world wide web, etc.

network model: IEEE LAN network model: IEEE LAN modelmodel

complements ISO model for LAN specific networks;

more specific in data link, physical layers; other layers unchanged

layers: physical MAC: media access control LLC: logical link control

network model: DoD model network model: DoD model

Alternative view; viewed networks as basic building blocks, thus not included in model

Fewer layers Applications

host-host (transport; now TCP )

internet layer (now IP)

network interface layer

purposes of networkspurposes of networks

resource sharing

increased reliability (redundancy, etc.)

efficiency

communications

future applications: voice, video, data, images, appliances, .... ?

basic network servicesbasic network services

e-mail

file transfers (ftp, etc)

remote login (rlogin, telnet)

WWW (web)

network ing industrynetwork ing industry

historically two separate and very different industries -- computers and communications

computer industry: IBM, DEC, Sun, Apple, Cray, SGI, Compaq, Dell, Gateway, Microsoft, etc

communications: AT&T, Sprint, MCI-WorldCom, RBOCs, GTE, other phone companies, etc.

network ing industrynetwork ing industry

these 2 industries have been merging signs of the merging

initial purpose of each signals importance of each to the other research labs Sun’s logo “the network is the computer”

industry sectors industry sectors

Computer Industry mainframes, “big” computers - IBM, Cray mid-size, workstations - Sun, SGI, (DEC,

Tandem) personal computers (manufacurers) -

Compaq, Dell, Gateway PCs - software - Microsoft semiconductors for PCs - Intel, AMD, NSM

industry sectorsindustry sectors Communications

long distance telephone (ATT, Sprint) local telephone (Pacific Bell, etc.) telecom. equipment (Lucent, Nor.

Telecom) telco eqmt (Lucent, etc.) data; internet (Cisco, 3Com)

internet service providers (AOL, etc) radio, wireless data, satelite, etc

standards for networksstandards for networks

reasons for standards

advantages

disadvantages

standards organizations

communication protocolscommunication protocols

protocol: the algorithm or procedure used for communication between processes at the same layer

examples: telephone call; e-mail

protocol processes make use of lower layers as a service.

heart of communications process

communication protocolscommunication protocols some things protocols do

bit interpretation to signals

group bits into messages

error detection and correction

synchronization

make more efficient use of networks facilities

communication protocolscommunication protocols

three basic phases of data communications1. connection establishment2. data transfer3. connection termination

connection-oriented/connectionless